The present invention relates to self-securing fasteners to prevent unwanted loosening of a fastener, and more particularly to a locking device for securing a nut to a fitting assembly of a fluid-coupling.
A problem associated with the use of nuts with fasteners and couplings is that of the nut backing out or loosening. The problem has been associated with vibrational, environmental, and other dynamic factors, which cause short-term loss of pre-load and nut back-off.
This problem is particularly apparent in the aircraft industry. In a study conducted by the Society of Automotive Engineers (SAE), 22% of fluid fittings that contained leakage were attributed to loose fittings due to nut back-off.
The prior art includes products which have tried to address the problem. For example, locking washers, spring washers, prevailing torque threads, deformed threads, plastic thread inserts, anaerobic adhesives, double-nutting, and locking pins have been used for fasteners. For fluid fittings and the like, the most common method of preventing nut loosening is by using a xe2x80x9csafety wirexe2x80x9d, in which a length of stainless steel wire is attached to the nut of the fluid coupling via a small hole. The other end of the wire is tied to a nearby component such that the nut rotation in the loosening direction is resisted by the wire.
The safety wire device, however, is costly, since it is extremely labor intensive. A mechanic must take an extra step to insure the nut stays put by affixing the safety wire device to a nearby component after tightening the nut. Thereafter, an additional step must be taken to twist the wire to eliminate the slack. The method is also prone to produce dangerous foreign object damage, since the wires must be trimmedxe2x80x94the excess of which can end up in moving components causing damage. In addition, since the wires must be cut if the particular fitting requires maintenance and/or routine re-tightening, the cutting produces sharp wire ends which may snag other objects or a mechanic""s hands. The wires also may break while being twisted to remove slack.
Attempts have been made to improve on the safety wire method by attempting to secure the nut to the mating half (the male half) of the coupling. One such convention device is a Moeller fitting, which provides torque resistance to the nut by positioning a pattern of torque xe2x80x9cbumpsxe2x80x9d along the male end of the coupling and corresponding recesses positioned along the interior surface of the nut to receive these bumps when mating the male and female halves. This system, however, requires that both the male and female coupling components conform to the Moeller design; i.e., one must replace both the male and female halves in using the Moeller design.
The present invention presents a new and unique device for providing a nut that locks to the female coupling half of a fitting assembly. By including a nut-locking device on the female half of the fitting assembly, it can be used with standard male fittings made by all manufacturers and also retrofitted on fittings used in previously installed fluid systems. Thus, the more expensive, bulky components can remain intact and retrofitted with new locking female assemblies according to the present invention.
The present invention seizes on the concept of locking the nut to the female coupling half on which it is normally a component part. Thus, all manufacturing design dimensions, materials of construction and component pre-assembly are within the manufacturer""s control, insuring a high-quality assembly.
By locking the nut to the female component, reactional forces from a mated fitting are transmitted to and directly resisted by a length of tubing affixed to the rear end of the female assembly. The forces are transmitted to the length of tubing via the nut and a securing member used to secure the nut to the female assembly.
In addition, with the female assembly component being most often immovably affixed to the rigid tubing to which it is attached by welding or other affixing means, resistance to loosening is realized from the rigid tubing itself. The rigid tubing provides additional rotational resistance about the axis of the end fitting. This is especially true where the geometry of the tubing includes bends and clamps.
In situations where two fitting assemblies utilizing the nut-locking device according to the present invention are used at either end of any geometric complexity of tubing, including a substantially straight run of tubing, any loosening torque encountered at one end fitting is directly resisted by the nut-lock fitting at the other end. This scenario is depicted in FIGS. 9A and 9B. Loosening torque (negative rotation) from vibration or other dynamic effects applied to the nut of the female assembly at one end fitting actually tightens (provides positive rotation) the nut from the female assembly on the male counterpart on the other end fitting.
Thus, although the nut-locking device according to the present invention operates sufficiently to resist loosening in a single fitting assembly on the end of a bent-tube, or the like, the present invention more preferably operates as a complete system where a nut-locking, fitting assembly is affixed to both ends of a length of tubing (especially on straight runs of tubing).
The present invention can also be used with many types of fittings including beam seal fittings, swivel wire type and slip-on type, flared and flareless fittings.
It is a feature of the locking mechanism according to the present invention to provide more resistance to loosening of the nut from the fitting assembly, and more preferably at least 2.5 times the amount of back-off torque supplied by the existing safety wire method of preventing nut back-off.
Thus, it is an object of the present invention to provide a locking device for a fluid fitting assembly.
It is another object of the present invention to provide a fitting assembly in which the nut resists back-off.
It is another object of the present invention to provide a locking device for a fluid fitting assembly which can be retrofitted to existing male-ended fittings.
It is still yet another object of the present invention to provide a locking device for a fluid fitting which is simple in design, lighter, and smaller in size than the prior art devices.
To accomplish the foregoing objects and advantages, one aspect of the current invention provides a locking mechanism for a fitting assembly of a fluid coupling including a fitting body, a securing member rotationally locked to the fitting body and a nut having a plurality of openings in cooperative relation to engage the securing member. When the nut is threaded onto a corresponding mated fitting, the securing member is engaged with at least one of the openings thereby locking the nut to the fitting body.
In another aspect of the present invention, a locking mechanism for a fitting assembly for a coupling includes a fitting body having an outer surface and a central axis, a spring member affixed to the outer surface, the spring member having a pawl projecting from the outer surface, and a nut having a plurality of ratchet teeth in cooperative relation to engage the pawl when the nut is threaded onto a corresponding mated fitting. The nut is restrained by the fitting body from rotating in a thread loosening direction by the engagement of the pawl with the ratchet teeth.
In yet another aspect of the present invention, a locking mechanism for a tubular fluid fitting assembly includes a fitting body having an outer surface and a central axis, a spring member affixed to the outer surface, with the spring member having a pawl projecting from the outer surface, and a nut having a plurality of ratchet teeth in cooperative relation to engage the pawl when the nut is threaded onto a corresponding mated fitting. The nut is restrained by the fitting body from rotating in a thread loosening direction by the engagement of the pawl with the ratchet teeth. The locking mechanism according to this aspect also includes a release member rotatably affixed to the nut where the release member includes an internal diameter for surrounding the spring member and/or said fitting body. The internal diameter includes a recess for receiving the pawl in an extended state. The locking device according to this aspect further includes a sleeve slidably affixed to the female assembly and surrounding a portion of the nut, the sleeve includes a helical recess for receiving a guide member positioned on the outer surface of the release member, an alignment member rotatably affixed to the release member, the alignment member including a sleeve guide which is received in a corresponding slot within the sleeve and includes an internal diameter having a fitting body guide member positioned thereon for being received by a corresponding recess on the fitting body and/or the spring member. Forcing the sleeve away from the mated fitting in a direction substantially parallel to the central axis results in the guide member traveling within the helical recess thereby rotating the release member in a pawl-disengaging direction to disengage the pawl from the ratchet teeth.
In yet another aspect of the present invention, a locking tubing system includes a length of tubing lying in any geometric complexity including a substantially straight line, a first fitting body having a securing member rotationally locked thereto, the first fitting body affixed to one end of the length of tubing, a first nut having a plurality of openings in cooperative relation to engage the securing member, a second fitting body having a securing member rotationally locked thereto, the second fitting body affixed to the other end of the length of tubing, and a second nut having a plurality of openings in cooperative relation to engage the securing member. When the first nut and the second nut are threaded onto corresponding mated fittings, each of the securing members are engaged with at least one of the openings of the respective nuts thereby locking each nut to the respective fitting body.
In yet another aspect of the present invention, a locking mechanism for a fitting assembly of a coupling includes a fitting body having a central axis, a nut having a plurality of ratchet teeth positioned parallel to the central axis and positioned on a rear portion of the nut, a sleeve having a front side and a back side. The sleeve surrounds a portion of the fitting body, slidably attached thereto allowing for substantially linear movement only, and includes a plurality of recesses adjacent the front side. The recesses include a shape substantially corresponding to a shape of the ratchet teeth of the nut and are positioned in cooperative relation to engage the ratchet teeth when the nut is threaded onto a mated fitting. Threading of the nut onto the male fitting allows the ratchet teeth of the nut to move relative to the recesses of the sleeve and restrains the nut from moving in a loosening direction.
In yet another aspect of the present invention, a locking mechanism for a tubular fluid fitting assembly includes a fitting body having a central axis, a nut having a plurality of openings positioned thereon, a sleeve surrounding a portion of the nut, the sleeve including a rear end having an internal diameter for receiving the fitting body and the rear end including an inner surface having a securing member projecting out therefrom in a direction toward the nut and substantially parallel to the central axis of the fitting body. The securing member is received within one of the plurality of openings after the nut has substantially engaged a mated fitting.
In yet another aspect of the present invention, a method for locking a nut of a female assembly of a fluid coupling to a fitting body of the female assembly when the female assembly is mated to a corresponding male fitting. The female assembly also includes a securing member rotationally locked to the fitting body for engagement with a plurality of openings provided on the nut when the nut is threaded onto the male fitting. The method includes the steps of threading the male fitting into the nut and engaging the securing member with at least one of the plurality of openings.
These and other aspects and objects, and many of the attendant advantages of this invention will be readily appreciated and understood by reference to the following detailed description when considered in connection with the accompany drawings.